1. Field of the Invention
The present invention is related to the field of transmission members for worm gears and, more particularly, to a compact damping coupling mechanism for worms in geared actuators.
2. Description of the Related Art
A wide range of couplings and dampeners are known in the art. Dampeners are normally employed to reduce the shock loads when an actuator runs into a hard stop, and are made from rubber-like material that absorbs some of the shock energy. Couplings are used to allow the motor to run freely in the opposite direction after running into the hard stop, thereby building up some energy to break loose from a stall condition as the gear train, especially with worm gears, may have locked up due to the stall load.
Couplings and dampeners are normally employed between the worm and the motor, thus forcing the worm to be at a certain minimal distance from the motor, moving out the mating helical gear with the worm and wasting some space. In addition, couplings and damping elements are typically purchased components which thereafter require assembly to the motor shaft and the worm. A further disadvantage of such prior art elements lies in the fact that since the coupling/dampener is situated between the worm and the motor, the worm must be on a separate shaft, increasing the number of parts required for a complete assembly.
In view of the foregoing, one object of the present invention is to overcome the difficulties of high impact loads and break-free problems associated with a worm mounted to the shaft of a DC motor.
Another object of the invention is to provide a damping coupling mechanism that requires a minimal number of parts, simplifying manufacturing and reducing cost.
A further object of the invention is a damping coupling mechanism for worms in geared actuators in which the worm gearing is located adjacent the motor, reducing space requirements.
Yet a further object of the invention is an integrated damping and coupling assembly that utilizes many standard parts to ease manufacturing requirements and minimize cost.
In accordance with this and other objects, the present invention is directed to a space-saving damping coupling assembly for use in geared actuators. The damping coupling assembly includes a worm, a thrust ring, a coupling washer and O-rings. The thrust ring is press-fitted to the motor shaft closest to the motor, followed by the slip-fit worm. The worm is held in place on the shaft by the coupling washer. Coupling elements on the worm fit cooperatively with torque-transmitting portions on the washer, with the interface between the worm and washer being cushioned by the O-rings fitted to the torque-transmitting portions. Torque from rotation of the motor shaft is transmitted to the worm through the washer, with the O-rings compressing to absorb shock. Before transmitting torque, the motor shaft is allowed to turn relative to the worm for a fraction of a revolution to gain inertia and speed to break loose a jammed gear train.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.